In general, a microwave oven is a cooking appliance for cooking food by applying microwave generated from a variety of electric parts into a cooking chamber. Recently, a microwave oven with a heater as a heating source in addition to microwave to cook a variety of foods has been launched.
FIG. 8 is an exploded perspective view showing a major portion of a microwave oven according to a prior art.
As shown in the figure, a cooking chamber 711 is provided within a cavity assembly 710 of the microwave oven. In addition, a porous portion 715 is provided in a side of an upper plate 713 of the cavity assembly 710 corresponding to the ceiling of the cooking chamber 711. The porous portion 715 is formed to have a plurality of holes bored through the upper plate 713 in the form of a generally rectangular shape.
In addition, an insulator 717 is installed on an upper surface of the upper plate 713. A heater opening portion 718 is formed in a portion of the insulator 717 corresponding to the porous portion 715. The heater opening portion 718 is a portion through which light and/or heat generated in a heater assembly 721 is supplied into the cooking chamber 711.
Also, a heater base 719 is provided on a portion of the insulator 717 corresponding to an inner peripheral portion of the heater opening portion 718. The heater base 719 is a portion to which the heater assembly 721 is fixed. The heater base 719 is shaped in a rectangular frame, and extension ribs 19R(=>719R) extending downward are provided on an inner peripheral portion of the heater base 719.
The heater base 719 is equipped with the heater assembly 721. The heater assembly 721 serves to heat food in the cooking chamber 711 by generating light and/or heat by applying power to the heater assembly 721. The heater assembly 721 is provided with a pair of heaters H7 and H7′ for substantially generating light and/or heat. The heaters H7 and H7′ may consist of, for example, a halogen heater and a ceramic heater.
The heaters H7 and H7′ are respectively fixed to an upper surface of a heater supporter 723. The heater supporter 723, which is shaped in a rectangular frame, is fixed to the heater base 719 with the heaters H7 and H7′ fixed to the upper surface of the heater supporter 723.
A reflecting plate 725 is provided above the heaters H7 and H7′. The reflecting plate 725 serves to reflect the light and/or heat of the heaters H7 and H7′ toward the interior of the cooking chamber 711. The reflecting plate 725 is provided with a plurality of vents 725H. The vents 725H allow a portion of airflow generated from a cooling fan assembly (not shown) to be introduced through the vents to cool the heaters H7 and H7′.
In addition, a pair of shield covers 727 and 729 are provided above the reflecting plate 725. The shield covers 727 and 729 serve to prevent that microwave generated in electric parts and applied into the cooking chamber 711 leaks to the outside through the porous portion 715. Unexplained reference numeral S7 designates a screw for fixing the heater assembly 721 to the heater base 719.
However, the microwave oven according to the above prior art has the following problems.
In the prior art, there are provided a plurality of the shield covers 727 and 729 in order to prevent microwave applied into the cooking chamber 711 from leaking to the outside through the porous portion 715. However, there is a disadvantage in that only the shield covers 727 and 729 cannot sufficiently prevent the microwave from leaking through the porous portion 715.